This invention relates to a car stabilizer and a method for manufacturing the same.
In this invention, a starting material for a stabilizer is a straight material in the shape of, e.g., a pipe which is formed of carbon steel with a carbon content of 0.10% to 0.35%, i.e., low-carbon steel.
A stabilizer 1 of this type used in a car suspension system has a form represented by a solid line in FIG. 1. As shown in FIG. 1, both end portions of the stabilizer 1 are coupled to their corresponding suspension units represented by broken lines so that the stabilizer 1 serves to stabilize a car when it makes a turn.
Prior art stabilizers of this construction have long been formed from solid steel materials. Recently, however, pipe materials have been used in order to contribute to lightweight car design.
These stabilizers are conventionally manufactured in accordance with the steps illustrated in FIG. 2. A straight material is bent into a predetermined shape in a bending process A as a first step, and then heat-treated in a quenching process B as a second step and then tempered in a tempering process C as a third step. Distortion of the material caused by the processing in these steps is corrected in a reforming process D as a fourth step, shot-peened as required in a process E, and coated and treated against rust in a coating process F as a final step. Thus, a stabilizer is obtained as a final product.
According to the prior art manufacturing method, as described above, the material is heat-treated in the second and third steps B anc C after it is bent in the first step A. Therefore, it requires large-sized equipment to place the bent piece in a furnace for heat treatment. A typical example of the furnace is a heavy-oil furnace which may be used for heat treatment of spring materials. The use of the heavy-oil furnace, however, constitutes an excessive expenditure of working energy. Since the heat treatment is performed in the steps B and C after the bending process in the first step A, the subsequent reforming process D becomes essential to the prior art manufacturing method, requiring additional time and labor.